Optical imaging system

ABSTRACT

An optical imaging system includes first through seventh lenses. The first lens includes positive refractive power, the second lens includes a positive refractive power, the third lens includes a negative refractive power, an object-side surface thereof being convex, the fourth lens includes a positive refractive power, the fifth lens includes a negative refractive power, the sixth lens includes a negative refractive power, and the seventh lens includes a negative refractive power and having an inflection point formed on an image-side surface thereof. The first to seventh lenses are sequentially disposed from an object side toward an imaging plane.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation of U.S. application Ser. No.15/292,369 filed on Oct. 13, 2016 which claims benefit under 35 USC119(a) of Korean Patent Application No. 10-2016-0010776 filed on Jan.28, 2016 in the Korean Intellectual Property Office, the disclosure ofwhich is incorporated herein by reference in its entirety.

BACKGROUND 1. Field

The following description relates to an optical imaging system thatincludes seven lenses.

2. Description of Related Art

A monitoring camera for an unmanned aerial vehicle is commonly used tomonitor a wide region, and a distance from such a monitoring camera to atarget to be monitored may be significantly large. Therefore, suchmonitoring camera requires an optical imaging system that has a widefield of view and in which a high level of resolution is realized.Similarly, a monitoring camera for a vehicle is used to capture imagesof vehicles at a front and at a rear of the vehicle. Therefore, amonitoring camera for such vehicle requires an optical imaging system inwhich a high level of resolution is realized.

An optical imaging system containing lenses formed of glass enables acamera having a high level of resolution to be realized. However, suchan optical imaging system including lenses made of glass has asignificantly heavier weight than an optical imaging system containinglenses made of plastic, thus, making it difficult to mount the opticalimaging system with lenses formed of glass in a small terminal.

In contrast, an optical imaging system including lenses made of plasticis relatively lightweight. However, it may be difficult to realize ahigher level of resolution with an optical imaging system includinglenses made of plastic than that of an optical imaging system includinglenses made of glass. Therefore, there is a need to develop an opticalimaging system that can realize a high level of resolution, while beinglightweight.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used as an aid in determining the scope of the claimed subjectmatter.

An aspect of the present disclosure may provide an optical imagingsystem having a high level of resolution.

In accordance with an embodiment, there may be provided an opticalimaging system, including: a first lens including a positive refractivepower; a second lens including a positive refractive power; a third lensincluding a negative refractive power, an object-side surface of thethird lens being convex; a fourth lens including a positive refractivepower; a fifth lens including a negative refractive power; a sixth lensincluding a negative refractive power; and a seventh lens including anegative refractive power and including an inflection point formed on animage-side surface thereof, wherein the first to seventh lenses aresequentially disposed from an object side toward an imaging plane.

An object-side surface of the first lens may be convex, and animage-side surface of the first lens may be concave.

An object-side surface and an image-side surface of the second lens maybe convex.

An image-side surface of the third lens may be concave.

An object-side surface and an image-side surface of the fourth lens maybe convex.

An object-side surface of the fifth lens may be concave, and animage-side surface of the fifth lens may be convex.

An object-side surface of the sixth lens may be convex, and animage-side surface of the sixth lens may be concave.

An object-side surface of the seventh lens may be convex, and animage-side surface of the seventh lens may be concave.

The optical imaging system may also include 0<f1/f<2.0, in which f is anoverall focal length of the optical imaging system and f1 is a focallength of the first lens.

The optical imaging system may also include 0<f2/f<1.5, in which f is anoverall focal length of the optical imaging system and f2 is a focallength of the second lens.

The optical imaging system may also include −3.0<f3/f<−1.0, in which fis an overall focal length of the optical imaging system and f3 is afocal length of the third lens.

The optical imaging system may also include 3.0<|f4/f|, in which f is anoverall focal length of the optical imaging system and f4 is a focallength of the fourth lens.

The optical imaging system may also include 1.3<f1/f2, in which f1 is afocal length of the first lens and f2 is a focal length of the secondlens.

The optical imaging system may also include −2.0<f2/f3<0, in which f2 isa focal length of the second lens and f3 is a focal length of the thirdlens.

The optical imaging system may also include r11/f<0, in which is anoverall focal length of the optical imaging system and r11 is a radiusof curvature of an image-side surface of the fifth lens.

The first to seventh lenses may be spaced apart from each other atpredetermined gaps or distances therebetween.

The optical imaging system may also include V1−V2<25, 25<V1−V3<45, and25<V1−V5<45, in which V1 is an Abbe number of the first lens, V2 is anAbbe number of the second lens, V3 is an Abbe number of the third lens,and V5 is an Abbe number of the fifth lens.

The optical imaging system may also include f5/f<0, f6/f<0, and f7/f<0,of which f is an overall focal length of the optical imaging system, f5is a focal length of the fifth lens, f6 is a focal length of the sixthlens, and f7 is a focal length of the seventh lens.

The optical imaging system may also include OAL/f<1.4, BFL/f<0.4,D12/f<0.1, and 0.2<r7/f<1.5, of which f is an overall focal length ofthe optical imaging system, OAL is a distance from the object-sidesurface of the first lens to the imaging plane, BFL is a distance fromthe image-side surface of the seventh lens to the imaging plane, D12 isa distance from an image-side surface of the first lens to anobject-side surface of the second lens, and r7 is a radius of curvatureof an image-side surface of the third lens.

In accordance with an embodiment, there is provided an optical imagingsystem, including: a first lens; a second lens including a convexobject-side surface and a convex image-side surface; a third lens; afourth lens; a fifth lens including a negative refractive power; a sixthlens including a negative refractive power; and a seventh lens includinga convex object-side surface and including an inflection point formed onan image-side surface thereof, wherein the first to seventh lenses aresequentially disposed from an object side toward an imaging plane.

Other features and aspects will be apparent from the following detaileddescription, the drawings, and the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view of an optical imaging system, according to a firstembodiment;

FIG. 2 are graphs representing aberration curves of the optical imagingsystem illustrated in FIG. 1;

FIG. 3 is a table representing characteristics of lenses of the opticalimaging system illustrated in FIG. 1;

FIG. 4 is a table representing aspherical characteristics of the opticalimaging system illustrated in FIG. 1;

FIG. 5 is a view of an optical imaging system, according to a secondembodiment;

FIG. 6 are graphs representing aberration curves of the optical imagingsystem illustrated in FIG. 5;

FIG. 7 is a table representing characteristics of lenses of the opticalimaging system illustrated in FIG. 5;

FIG. 8 is a table representing aspherical characteristics of the opticalimaging system illustrated in FIG. 5;

FIG. 9 is a view of an optical imaging system, according to a thirdembodiment;

FIG. 10 shows graphs representing aberration curves of the opticalimaging system illustrated in FIG. 9;

FIG. 11 is a table representing characteristics of lenses of the opticalimaging system illustrated in FIG. 9;

FIG. 12 is a table representing aspherical characteristics of theoptical imaging system illustrated in FIG. 9;

FIG. 13 is a view of an optical imaging system, according to a fourthembodiment;

FIG. 14 shows graphs representing aberration curves of the opticalimaging system illustrated in FIG. 13;

FIG. 15 is a table representing characteristics of lenses of the opticalimaging system illustrated in FIG. 13; and

FIG. 16 is a table representing aspherical characteristics of theoptical imaging system illustrated in FIG. 13.

Throughout the drawings and the detailed description, unless otherwisedescribed, the same drawing reference numerals will be understood torefer to the same elements, features, and structures. The relative sizeand depiction of these elements may be exaggerated for clarity,illustration, and convenience.

DETAILED DESCRIPTION

The following detailed description is provided to assist the reader ingaining a comprehensive understanding of the methods, apparatuses,and/or systems described herein. However, various changes,modifications, and equivalents of the methods, apparatuses, and/orsystems described herein will be apparent to one of ordinary skill inthe art. The sequences of operations described herein are merelyexamples, and are not limited to those set forth herein, but may bechanged as will be apparent to one of ordinary skill in the art, withthe exception of operations necessarily occurring in a certain order.Also, descriptions of functions and constructions that are well known toone of ordinary skill in the art may be omitted for increased clarityand conciseness.

The features described herein may be embodied in different forms, andare not to be construed as being limited to the examples describedherein. Rather, the examples described herein have been provided so thatthis disclosure will be thorough and complete, and will convey the fullscope of the disclosure to one of ordinary skill in the art.

The features described herein may be embodied in different forms, andare not to be construed as being limited to the examples describedherein. Rather, the examples described herein have been provided so thatthis disclosure will be thorough and complete, and will convey the fullscope of the disclosure to one of ordinary skill in the art.

It will be understood that, although the terms first, second, third,etc. may be used herein to describe various lenses, these lenses shouldnot be limited by these terms. These terms are only used to distinguishone lens from another lens. These terms do not necessarily imply aspecific order or arrangement of the lenses. Thus, a first lensdiscussed below could be termed a second lens without departing from theteachings description of the various embodiments.

Example embodiments of the present disclosure will now be described indetail with reference to the accompanying drawings.

In addition, a surface of each lens closest to an object is referred toas a first surface or an object-side surface, and a surface of each lensclosest to an imaging surface is referred to as a second surface or animage-side surface. Further, all numerical values of radii of curvature,thicknesses/distances, TTLs, Y (½ of a diagonal length of the imagingplane), and focal lengths, and other parameters of the lenses arerepresented in millimeters (mm).

A person skilled in the relevant art will appreciate that other units ofmeasurement may be used. Further, in the present specification, allradii of curvature, thicknesses, OALs (optical axis distances from thefirst surface of the first lens to the image sensor (OALs), a distanceon the optical axis between the stop and the image sensor (SLs), imageheights (IMGHs) (image heights), and black focus lengths (BFLs) (backfocus lengths) of the lenses, an overall focal length of an opticalsystem, and a focal length of each lens are indicated in millimeters(mm). Further, thicknesses of lenses, gaps between the lenses, OALs, andSLs are distances measured based on an optical axis of the lenses.

In addition, in an embodiment, shapes of lenses are described andillustrated in relation to optical axis portions of the lenses.

A surface of a lens being convex means that an optical axis portion of acorresponding surface is convex, and a surface of a lens being concavemeans that an optical axis portion of a corresponding surface isconcave. Therefore, in a configuration in which one surface of a lens isdescribed as being convex, an edge portion of the lens may be concave.Likewise, in a configuration in which one surface of a lens is describedas being concave, an edge portion of the lens may be convex. In otherwords, a paraxial region of a lens may be convex, while the remainingportion of the lens outside the paraxial region is either convex,concave, or flat. Further, a paraxial region of a lens may be concave,while the remaining portion of the lens outside the paraxial region iseither convex, concave, or flat.

In addition, in an embodiment, thicknesses and radii of curvatures oflenses are measured in relation to optical axes of the correspondinglenses.

An optical system, according to an embodiment, includes six lenses. Asan example, the optical system may include a first lens, a second lens,a third lens, a fourth lens, a fifth lens, a sixth lens, and a seventhlens. The lens module may include from four lenses up to six lenseswithout departing from the scope of the embodiments herein described. Inaccordance with an illustrative example, the embodiments described ofthe optical system include six lenses with a refractive power. However,a person of ordinary skill in the relevant art will appreciate that thenumber of lenses in the optical system may vary, for example, betweentwo to six lenses, while achieving the various results and benefitsdescribed hereinbelow. Also, although each lens is described with aparticular refractive power, a different refractive power for at leastone of the lenses may be used to achieve the intended result.

In the optical system, according to embodiments, the first to seventhlenses are formed of materials including glass, plastic or other similartypes of polycarbonate materials. In another embodiment, at least one ofthe first through sixth lenses is formed of a material different fromthe materials forming the other first through sixth lenses.

The first to seventh lenses may be formed of materials having arefractive index different from that of air. For example, the first toseventh lenses are formed of plastic or glass. At least one of the firstto seventh lenses may have an aspherical shape. In one example, only theseventh lens of the first to seventh lenses has an aspherical shape. Inaddition, at least one surface of all of the first to seventh lenses maybe aspherical. Here, an aspherical surface of each lens may berepresented by the following Equation 1:

$\begin{matrix}{z = {\frac{{cr}^{2}}{1 + \sqrt{1 - {\left( {1 + k} \right)c^{2}r^{2}}}} + {Ar}^{4} + {Br}^{6} + {Cr}^{8} + {Dr}^{10} + {Er}^{12} + {Fr}^{14} + {Gr}^{16} + {Hr}^{18} + {{Jr}^{20}.}}} & \left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack\end{matrix}$

In Equation 1, c is an inverse of a radius of curvature of the lens, kis a conic constant, r is a distance from a certain point on anaspherical surface of the lens to an optical axis, A to J are asphericalconstants, and Z (or SAG) is a distance between the certain point on theaspherical surface of the lens at the distance r and a tangential planemeeting the apex of the aspherical surface of the lens.

An optical imaging system, in accordance with an embodiment, includes aplurality of lenses having refractive power. For example, the opticalimaging system includes seven lenses. In the following sections, thefirst to seventh lenses configuring the optical imaging system will bedescribed in detail.

The first lens has a refractive power, such as a positive refractivepower or a negative refractive power. For example, the first lens has apositive refractive power. One surface of the first lens may be convex.For example, an object-side surface of the first lens is convex. Thefirst lens may have an aspherical surface. For example, both surfaces ofthe first lens are aspherical. The first lens may be formed of amaterial having high light transmissivity and excellent workability. Forexample, the first lens is formed of plastic. However, a material of thefirst lens is not limited to plastic. For example, the first lens mayalso be formed of glass. The first lens may have a predetermined focallength. For example, a focal length of the first lens is predeterminedto be in a range of 6.0 to 8.0.

The second lens may have refractive power, such as a positive refractivepower or a negative refractive power. For example, the second lens has apositive refractive power. At least one surface of the second lens maybe convex. For example, both surfaces of the second lens are convex. Thesecond lens may have an aspherical surface. For example, both surfacesof the second lens are aspherical. The second lens may be formed of amaterial having high light transmissivity and excellent workability. Forexample, the second lens is formed of plastic. However, a material ofthe second lens is not limited to plastic. For example, the second lensmay also be formed of glass. The second lens may have a predeterminedfocal length. For example, a focal length of the second lens ispredetermined to be in a range of 3.5 to 5.5.

The third lens may have refractive power, such as a positive refractivepower or a negative refractive power. For example, the third lens has anegative refractive power. One surface of the third lens may be convex.For example, an object-side surface of the third lens is convex. Thethird lens may have an aspherical surface. For example, both surfaces ofthe third lens are aspherical. The third lens may be formed of amaterial having high light transmissivity and excellent workability. Forexample, the third lens is formed of plastic. However, a material of thethird lens is not limited to plastic. For example, the third lens mayalso be formed of glass. The third lens may have a high refractiveindex. For example, a refractive index of the third lens is 1.60 ormore. The third lens may have a predetermined focal length. For example,a focal length of the third lens is predetermined to be in a range of−6.0 to −4.0.

The fourth lens may have refractive power, such as a positive refractivepower or a negative refractive power. For example, the fourth lens has apositive refractive power. At least one surface of the fourth lens maybe convex. For example, both surfaces of the fourth lens are convex. Thefourth lens may have an aspherical surface. For example, both surfacesof the fourth lens are aspherical. The fourth lens may be formed of amaterial having high light transmissivity and excellent workability. Forexample, the fourth lens is formed of plastic. However, a material ofthe fourth lens is not limited to plastic. For example, the fourth lensmay also be formed of glass. The fourth lens may have a high refractiveindex. For example, a refractive index of the fourth lens is 1.60 ormore. The fourth lens may have a predetermined focal length. Forexample, a focal length of the fourth lens is predetermined to be in arange of 12.0 to 17.0.

The fifth lens may have refractive power, such as a positive refractivepower or a negative refractive power. For example, the fifth lens has anegative refractive power. At least one surface of the fifth lens may beconcave. For example, an object-side surface of the fifth lens isconcave. The fifth lens may have an aspherical surface. For example,both surfaces of the fifth lens are aspherical. The fifth lens may beformed of a material having high light transmissivity and excellentworkability. For example, the fifth lens is formed of plastic. However,a material of the fifth lens is not limited to plastic. For example, thefifth lens may also be formed of glass. The fifth lens may have a highrefractive index. For example, a refractive index of the fifth lens is1.60 or more. The fifth lens may have a predetermined focal length. Forexample, a focal length of the fifth lens is predetermined to be in arange of −90.0 or less.

The sixth lens may have refractive power, such as a positive refractivepower or a negative refractive power. For example, the sixth lens has anegative refractive power. At least one surface of the sixth lens may beconvex. For example, an object-side surface of the sixth lens is convex.The sixth lens may have an aspherical surface and, as shown in FIG. 1,for example, end points of the sixth lens may extend towards theobject-side encasing, covering, encapsulating, or over the first throughfifth lenses. For example, both surfaces of the sixth lens may beaspherical. The sixth lens may have an inflection point. For example,one or more inflection points is formed on an image-side surface of thesixth lens. The sixth lens may be formed of a material having high lighttransmissivity and excellent workability. For example, the sixth lens isformed of plastic. However, a material of the sixth lens is not limitedto plastic. For example, the sixth lens may also be formed of glass. Thesixth lens may have a predetermined focal length. For example, a focallength of the sixth lens is predetermined to be in a range of −90.0 orless.

The seventh lens may have refractive power, such as a positiverefractive power or a negative refractive power. For example, theseventh lens has a negative refractive power. At least one surface ofthe seventh lens may be convex. For example, an object-side surface ofthe seventh lens is convex. The seventh lens may have an asphericalsurface. For example, both surfaces of the seventh lens are aspherical.The seventh lens may have an inflection point. For example, one or moreinflection points is formed on an image-side surface of the seventhlens. The seventh lens may be formed of a material having high lighttransmissivity and excellent workability. For example, the seventh lensis formed of plastic. However, a material of the seventh lens is notlimited to plastic. For example, the seventh lens may also be formed ofglass. The seventh lens may have a predetermined focal length. Forexample, a focal length of the seventh lens is predetermined to be in arange of −15.0 or more.

In accordance with alternative examples, each of the first throughseventh lenses may be configured in an opposite refractive power fromthe configuration described above. For example, in an alternativeconfiguration, the first lens has a negative refractive power, thesecond lens has a negative refractive power, the third lens has apositive refractive power, the fourth lens has a negative refractivepower, the fifth lens has a positive refractive power, the sixth lenshas a positive refractive power, and the seventh lens has a positiverefractive power.

The optical imaging system may include a stop. For example, the opticalimaging system includes a first stop disposed adjacent to theobject-side surface of the first lens. In addition, the optical imagingsystem includes a second stop disposed between the second lens and thethird lens.

The optical imaging system includes an image sensor. The image sensor isconfigured to realize a high level of resolution. For example, a unitsize of pixels configuring the image sensor is 1.12 μm or less. Theimage sensor forms an imaging plane.

The optical imaging system may include a filter. For example, theoptical imaging system includes a filter disposed between the seventhlens and the image sensor. The filter may filter a partial wavelengthfrom incident light that is incident through the first to seventhlenses. For example, the filter filters an infrared wavelength of theincident light.

The optical imaging system satisfies the following ConditionalExpressions:

0<f1/f<2.0   [Conditional Expression 1]

V1−V2<25   [Conditional Expression 2]

25<V1−V3<45   [Conditional Expression 3]

25<V1−V5<45   [Conditional Expression 4]

0<f2/f<1.5   [Conditional Expression 5]

−3.0<f3/f<−1.0   [Conditional Expression 6]

3.0<|f4/f|  [Conditional Expression 7]

f5/f<0   [Conditional Expression 8]

f6/f<0   [Conditional Expression 9]

f7/f<0   [Conditional Expression 10]

OAL/f<1.4   [Conditional Expression 11]

1.3<f1/f2   [Conditional Expression 12]

−2.0<f2/f3<0   [Conditional Expression 13]

BFL/f<0.4   [Conditional Expression 14]

D12/f<0.1   [Conditional Expression 15]

0.2<r7/f<1.5   [Conditional Expression 16]

r11/f<0.   [Conditional Expression 17]

Here, f is an overall focal length of the optical imaging system, f1 isa focal length of the first lens, f2 is a focal length of the secondlens, f3 is a focal length of the third lens, f4 is a focal length ofthe fourth lens, f5 is a focal length of the fifth lens, f6 is a focallength of the sixth lens, and f7 is a focal length of the seventh lens.Furthermore, V1 is an Abbe number of the first lens, V2 is an Abbenumber of the second lens, V3 is an Abbe number of the third lens, andV5 is an Abbe number of the fifth lens. In addition, OAL is a distancefrom the object-side surface of the first lens to the imaging plane, BFLis a distance from the image-side surface of the seventh lens to theimaging plane, and D12 is a distance from an image-side surface of thefirst lens to an object-side surface of the second lens. In theconditional expressions, r7 is a radius of curvature of an image-sidesurface of the third lens, and r11 is a radius of curvature of animage-side surface of the fifth lens.

Conditional Expression 1 is an equation to limit the refractive power ofthe first lens. For example, in an example in which f1/f is outside ofthe numerical range of Conditional Expression 1, the first lens wouldmake it difficult to distribute the refractive power of other lenses.

Conditional Expressions 2 to 4 are equations to improve chromaticaberrations of the optical imaging system. For example, in a case inwhich V1-V2, V1-V3, and V1-V5 are outside of the numerical ranges ofConditional Expressions 2 to 4, respectively, it would be difficult toimprove chromatic aberrations of the optical imaging system.

Conditional Expressions 5 to 7 are equations to improve aberrations ofthe optical imaging system. For example, in a case in which f2/f, f3/f,and |f4/f| are outside of the numerical ranges of ConditionalExpressions 5 to 7, respectively, the refractive power of the second tofourth lenses of the optical imaging system is excessively small, suchthat it would be difficult to correct aberrations of the optical imagingsystem.

Conditional Expressions 8 to 10 are equations to limit the refractivepower of the optical imaging system. For example, in a case in whichf5/f, f6/f, and f7/f are outside of the numerical ranges of ConditionalExpressions 8 to 10, respectively, the fifth to seventh lenses wouldmake it difficult to design the optical imaging system.

Conditional Expressions 11 and 14 are equations to miniaturize theoptical imaging system. For example, in a case in which OAUf and BFUfare outside of the numerical ranges of Conditional Expressions 11 and14, respectively, a distance from the first lens to the imaging plane isexcessively long, such that it would be difficult to miniaturize theoptical imaging system.

Conditional Expressions 12 and 13 are equations to reduce aberrations ofthe optical imaging system. For example, in a case in which f1/f2 andf2/f3 are outside of the numerical ranges of Conditional Expressions 12and 13, respectively, the refractive power of a specific lens of thefirst to third lenses is excessively large, such that aberrationcharacteristics of the optical imaging system would increase.

Conditional Expressions 14 to 17 are equations to improve aberrationcharacteristics of the optical imaging system.

In an example in which Conditional Expressions 14 to 17 are satisfied,the optical imaging system realizes a bright image. For example, theoptical imaging system has an F number of 1.80 or less. In addition, theoptical imaging system, according to an embodiment, realizes aresolution of 13 megapixels or more.

Next, optical imaging systems, according to several embodiments, will bedescribed.

An optical imaging system, according to a first embodiment, will bedescribed with reference to FIG. 1.

The optical imaging system 100, according to the first embodiment,includes an optical system including a first lens 110, a second lens120, a third lens 130, a fourth lens 140, a fifth lens 150, a sixth lens160, and a seventh lens 170. The first to seventh lenses 110 to 170 aresequentially disposed from an object toward an imaging plane 190. Thefirst to seventh lenses 110 to 170 are spaced apart from each other atpredetermined gaps or distances therebetween. For example, the first toseventh lenses 110 to 170 do not contact lenses neighboring thereto in aparaxial region. In an alternative embodiment, the second and the thirdlenses 120 and 130 may contact at a point of the optical axis or in aparaxial region.

The optical imaging system 100 includes a filter 180 and an imagesensor. The filter 180 is disposed between the seventh lens 170 and theimage sensor. The image sensor converts light refracted by the first toseventh lenses 110 to 170 into electrical signals, and provides animaging plane 190 required for the optical imaging system 100.

The optical imaging system 100 includes one or more stops ST1 and ST2. Afirst stop ST1 is disposed adjacent to an object-side surface of thefirst lens, and a second stop ST2 is disposed between the second lensand the third lens. For reference, the second stop ST2 may be omitted,if necessary.

In an embodiment, the first lens 110 has a positive refractive power,and the object-side surface thereof is convex, while an image-sidesurface thereof is concave. The second lens 120 has a positiverefractive power, and both surfaces thereof are convex. The third lens130 has a negative refractive power, and an object-side surface thereofis convex and an image-side surface thereof is concave. The fourth lens140 has a positive refractive power, and both surfaces thereof areconvex. The fifth lens 150 has a negative refractive power, and anobject-side surface thereof is concave, while an image-side surfacethereof is convex. The sixth lens 160 has a negative refractive power,and an object-side surface thereof is convex and an image-side surfacethereof is concave. One or more inflection points is formed on bothsurfaces of the sixth lens 160. The seventh lens 170 has a negativerefractive power, and an object-side surface thereof is convex, while animage-side surface thereof is concave. One or more inflection points isformed on both surfaces of the seventh lens 170.

The optical imaging system configured as described above representsaberration characteristics as illustrated in FIG. 2. For reference, IMGHT of FIG. 2 refers to ½ of a diagonal length of the imaging plane. Inan embodiment, IMG HT is 3.51. FIGS. 3 and 4 are tables representingcharacteristics of lenses and aspherical characteristics of the opticalimaging system, according to the first embodiment, respectively.

Next, an optical imaging system, according to a second embodiment, willbe described with reference to FIG. 5.

The optical imaging system 200, according to the second embodiment,includes an optical system including a first lens 210, a second lens220, a third lens 230, a fourth lens 240, a fifth lens 250, a sixth lens260, and a seventh lens 270. The first to seventh lenses 210 to 270 aresequentially disposed from an object toward an imaging plane 290. Thefirst to seventh lenses 210 to 270 are also disposed to be spaced apartfrom each other at predetermined gaps. For example, the first to seventhlenses 210 to 270 do not contact lenses neighboring thereto in aparaxial region. In an alternative embodiment, the second and the thirdlenses 220 and 230 may contact at a point of the optical axis or in aparaxial region.

The optical imaging system 200 includes a filter 280 and an imagesensor. The filter 280 is disposed between the seventh lens 270 and theimage sensor. The image sensor converts light refracted by the first toseventh lenses 210 to 270 into electrical signals, and provides animaging plane 290 required for the optical imaging system 200.

The optical imaging system 200 includes one or more stops ST1 and ST2. Afirst stop ST1 is disposed adjacent to an object-side surface of thefirst lens, and a second stop ST2 is disposed between the second lensand the third lens. For reference, the second stop ST2 may be omitted,if necessary.

In an embodiment, the first lens 210 has a positive refractive power,the object-side surface thereof is convex, and an image-side surfacethereof is concave. The second lens 220 has a positive refractive power,and both surfaces thereof are convex. The third lens 230 has a negativerefractive power, an object-side surface thereof is convex, while animage-side surface thereof is concave. The fourth lens 240 has apositive refractive power, and both surfaces thereof are convex. Thefifth lens 250 has a negative refractive power, an object-side surfacethereof is concave, and an image-side surface thereof is convex. Thesixth lens 260 has a negative refractive power, while an object-sidesurface thereof is convex, and an image-side surface thereof is concave.One or more inflection points is formed on both surfaces of the sixthlens 260. The seventh lens 270 has a negative refractive power, while anobject-side surface thereof is convex and an image-side surface thereofis concave. One or more inflection points is formed on both surfaces ofthe seventh lens 270.

The optical imaging system configured as described above representsaberration characteristics as illustrated in FIG. 6. In an embodiment,IMG HT may be 3.51, as illustrated in FIG. 6. FIGS. 7 and 8 are tablesrepresenting characteristics of lenses and aspherical characteristics ofthe optical imaging system, according to the second embodiment,respectively.

An optical imaging system, according to a third embodiment, will bedescribed with reference to FIG. 9.

The optical imaging system 300, according to the third embodiment,includes an optical system including a first lens 310, a second lens320, a third lens 330, a fourth lens 340, a fifth lens 350, a sixth lens360, and a seventh lens 370. The first to seventh lenses 310 to 370 aresequentially disposed from an object toward an imaging plane 390. Thefirst to seventh lenses 310 to 370 are disposed to be spaced apart fromeach other at predetermined gaps. For example, the first to seventhlenses 310 to 370 do not contact lenses neighboring thereto in aparaxial region. In an alternative embodiment, the second and the thirdlenses 320 and 330 may contact at a point of the optical axis or in aparaxial region.

The optical imaging system 300 includes a filter 380 and an imagesensor. The filter 380 is disposed between the seventh lens 370 and theimage sensor. The image sensor converts light refracted by the first toseventh lenses 310 to 370 into electrical signals, and provides animaging plane 390 required for the optical imaging system 300.

The optical imaging system 300 includes one or more stops ST1 and ST2. Afirst stop ST1 is disposed adjacent to an object-side surface of thefirst lens, and a second stop ST2 is disposed between the second lensand the third lens. For reference, the second stop ST2 may be omitted,if necessary.

In an embodiment, the first lens 310 has a positive refractive power,the object-side surface thereof is convex, and an image-side surfacethereof is concave.

The second lens 320 has a positive refractive power, and both surfacesthereof are convex. The third lens 330 has a negative refractive power,an object-side surface thereof is convex and an image-side surfacethereof is concave. The fourth lens 340 has a positive refractive power,and both surfaces thereof are convex. The fifth lens 350 has a negativerefractive power, an object-side surface thereof is concave, while animage-side surface thereof is convex. The sixth lens 360 has a negativerefractive power, an object-side surface thereof is convex, and animage-side surface thereof is concave. One or more inflection points isformed on both surfaces of the sixth lens 360. The seventh lens 370 hasa negative refractive power, an object-side surface thereof is convex,and an image-side surface thereof is concave. One or more inflectionpoints is formed on both surfaces of the seventh lens 370.

The optical imaging system configured as described above representsaberration characteristics as illustrated in FIG. 10. In an embodiment,IMG HT may be 3.50, as illustrated in FIG. 10. FIGS. 11 and 12 aretables representing characteristics of lenses and asphericalcharacteristics of the optical imaging system, according to the thirdembodiment, respectively.

Following is a description of an optical imaging system according to afourth exemplary embodiment, with reference to FIG. 13.

The optical imaging system 400, according to the fourth embodimentincludes an optical system, including a first lens 410, a second lens420, a third lens 430, a fourth lens 440, a fifth lens 450, a sixth lens460, and a seventh lens 470. The first to seventh lenses 410 to 470 aresequentially disposed from an object toward an imaging plane 490. Thefirst to seventh lenses 410 to 470 are disposed to be spaced apart fromeach other at predetermined gaps. For example, the first to seventhlenses 410 to 470 do not contact lenses neighboring thereto in aparaxial region. In an alternative embodiment, the second and the thirdlenses 420 and 430 may contact at a point of the optical axis or in aparaxial region.

The optical imaging system 400 includes a filter 480 and an imagesensor. The filter 480 is disposed between the seventh lens 470 and theimage sensor. The image sensor converts light refracted by the first toseventh lenses 410 to 470 into electrical signals, and provides animaging plane 490 required for the optical imaging system 400.

The optical imaging system 400 includes one or more stops ST1 and ST2. Afirst stop ST1 is disposed adjacent to an object-side surface of thefirst lens, and a second stop ST2 is disposed between the second lensand the third lens. For reference, the second stop ST2 may be omitted,if necessary.

In an embodiment, the first lens 410 has a positive refractive power,the object-side surface thereof is convex, and an image-side surfacethereof is concave. The second lens 420 has a positive refractive power,and both surfaces thereof are convex. The third lens 430 has a negativerefractive power, while an object-side surface thereof is convex, and animage-side surface thereof is concave. The fourth lens 440 has apositive refractive power, and both surfaces thereof are convex. Thefifth lens 450 has a negative refractive power, an object-side surfacethereof is concave, and an image-side surface thereof is convex. Thesixth lens 460 has a negative refractive power, while an object-sidesurface thereof is convex, and an image-side surface thereof is concave.One or more inflection points is formed on both surfaces of the sixthlens 460. The seventh lens 470 has a negative refractive power, anobject-side surface thereof is convex, and an image-side surface thereofis concave. One or more inflection points is formed on both surfaces ofthe seventh lens 470.

The optical imaging system configured as described above representsaberration characteristics, as illustrated in FIG. 14. In an embodiment,IMG HT may be 3.51, as illustrated in FIG. 14. FIGS. 15 and 16 aretables representing characteristics of lenses and asphericalcharacteristics of the optical imaging system, according to the fourthembodiment, respectively.

Table 1 represents values of Conditional Expressions of the opticalimaging systems, according to the first to fourth embodiments.

TABLE 1 Conditional First Second Third Fourth Expression EmbodimentEmbodiment Embodiment Embodiment f1/f 1.641 1.650 1.653 1.652 V1-V2 0 00 0 V1-V3 34.60 34.60 34.60 34.60 V1-V5 30.10 30.10 30.10 30.10 f2/f1.036 1.030 1.030 1.030 f3/f −1.146 −1.148 −1.146 −1.146 |f4/f| 3.6763.550 3.550 3.196 f5/f −229.88 −114.94 −68.97 −22.99 f6/f −229.88−115.06 −68.97 −22.99 f7/f −2.013 −1.929 −2.010 −2.172 OAL/f 1.217 1.2131.215 1.215 f1/f2 1.584 1.602 1.605 1.604 f2/f3 −0.904 −0.897 −0.899−0.899 BFL/f 0.235 0.233 0.233 0.233 D12/f 0.038 0.038 0.038 0.039 r7/f0.526 0.527 0.526 0.526 r11/f −1.519 −1.670 −1.662 −1.465

As set forth above, according to embodiments, an optical imaging systemmay be mounted in a small terminal and include a high level ofresolution.

While this disclosure includes specific examples, it will be apparent toone of ordinary skill in the art that various changes in form anddetails may be made in these examples without departing from the spiritand scope of the claims and their equivalents. The examples describedherein are to be considered in a descriptive sense only, and not forpurposes of limitation. Descriptions of features or aspects in eachexample are to be considered as being applicable to similar features oraspects in other examples. Suitable results may be achieved if thedescribed techniques are performed in a different order, and/or ifcomponents in a described system, architecture, device, or circuit arecombined in a different manner and/or replaced or supplemented by othercomponents or their equivalents. Therefore, the scope of the disclosureis defined not by the detailed description, but by the claims and theirequivalents, and all variations within the scope of the claims and theirequivalents are to be construed as being included in the disclosure.

What is claimed is:
 1. An optical imaging system, comprising: a firstlens comprising a positive refractive power; a second lens comprising apositive refractive power; a third lens comprising a negative refractivepower, an object-side surface of the third lens being convex; a fourthlens comprising a positive refractive power; a fifth lens comprising anegative refractive power; a sixth lens comprising a negative refractivepower; and a seventh lens comprising a negative refractive power andcomprising an inflection point formed on an image-side surface thereof,wherein the first to seventh lenses are sequentially disposed from anobject side toward an imaging plane.
 2. The optical imaging system ofclaim 1, wherein an object-side surface of the first lens is convex, andan image-side surface of the first lens is concave.
 3. The opticalimaging system of claim 1, wherein an object-side surface and animage-side surface of the second lens are convex.
 4. The optical imagingsystem of claim 1, wherein an image-side surface of the third lens isconcave.
 5. The optical imaging system of claim 1, wherein anobject-side surface and an image-side surface of the fourth lens areconvex.
 6. The optical imaging system of claim 1, wherein an object-sidesurface of the fifth lens is concave, and an image-side surface of thefifth lens is convex.
 7. The optical imaging system of claim 1, whereinan object-side surface of the sixth lens is convex, and an image-sidesurface of the sixth lens is concave.
 8. The optical imaging system ofclaim 1, wherein an object-side surface of the seventh lens is convex,and an image-side surface of the seventh lens is concave.
 9. The opticalimaging system of claim 1, wherein 0<f1/f<2.0, in which f is an overallfocal length of the optical imaging system and f1 is a focal length ofthe first lens.
 10. The optical imaging system of claim 1, wherein0<f2/f<1.5, in which f is an overall focal length of the optical imagingsystem and f2 is a focal length of the second lens.
 11. The opticalimaging system of claim 1, wherein −3.0<f3/f<−1.0, in which f is anoverall focal length of the optical imaging system and f3 is a focallength of the third lens.
 12. The optical imaging system of claim 1,wherein 3.0<|f4/f|, in which f is an overall focal length of the opticalimaging system and f4 is a focal length of the fourth lens.
 13. Theoptical imaging system of claim 1, wherein 1.3<f1/f2, in which f1 is afocal length of the first lens and f2 is a focal length of the secondlens.
 14. The optical imaging system of claim 1, wherein −2.0<f2/f3<0,in which f2 is a focal length of the second lens and f3 is a focallength of the third lens.
 15. The optical imaging system of claim 1,wherein r11/f<0, in which is an overall focal length of the opticalimaging system and r11 is a radius of curvature of an image-side surfaceof the fifth lens.
 16. The optical imaging system of claim 1, whereinthe first to seventh lenses are spaced apart from each other atpredetermined gaps or distances therebetween.
 17. The optical imagingsystem of claim 1, wherein V1−V221 25, 25<V1−V3<45, and 25<V1−V5<45, inwhich V1 is an Abbe number of the first lens, V2 is an Abbe number ofthe second lens, V3 is an Abbe number of the third lens, and V5 is anAbbe number of the fifth lens.
 18. The optical imaging system of claim1, wherein f5/f<0, f6/f<0, and f7/f<0, of which f is an overall focallength of the optical imaging system, f5 is a focal length of the fifthlens, f6 is a focal length of the sixth lens, and f7 is a focal lengthof the seventh lens.
 19. The optical imaging system of claim 1, whereinOAL/f<1.4, BFL/f<0.4, D12/f<0.1, and 0.2<r7/f<1.5, of which f is anoverall focal length of the optical imaging system, OAL is a distancefrom the object-side surface of the first lens to the imaging plane, BFLis a distance from the image-side surface of the seventh lens to theimaging plane, D12 is a distance from an image-side surface of the firstlens to an object-side surface of the second lens, and r7 is a radius ofcurvature of an image-side surface of the third lens.